Hardness distribution and aging response associated with precipitation behavior in a laser pressure welded Al-Li alloy 2198

Abstract Although laser welded Al-Li alloys show great potential for application in aerospace industry, the detailed relationship between local hardness and complex microstructure remained unclear. In the present study, relationship between precipitation behavior and local hardness in a defect-free laser pressure weld of Al-Li alloy 2198 was systematically examined by transmission electron microscopy. Hardness profile of the laser pressure weld was reduced in the vicinity of the weld center, mainly explained by size and density of the strengthening precipitates. Moreover, post-weld aging increased the density of strengthening precipitates in the precipitate-dissolved regions, increasing their hardness values markedly. On the other hand, a few precipitates were formed in the precipitate-coarsened regions during post-weld aging, which slightly increased the local hardness. The variation in hardness during post-weld aging could be well correlated with the precipitation behavior in each region of the laser pressure weld.